package io.github.dunwu.springboot.snake;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 * Sets up the timer for the multi-player snake game WebSocket example.
 */
public final class SnakeTimer {

    private static final long TICK_DELAY = 100;

    private static final Object MONITOR = new Object();

    private static final Logger log = LoggerFactory.getLogger(SnakeTimer.class);

    private static final ConcurrentHashMap<Integer, Snake> snakes = new ConcurrentHashMap<>();

    private static Timer gameTimer = null;

    private SnakeTimer() {
    }

    public static void addSnake(Snake snake) {
        synchronized (MONITOR) {
            if (snakes.isEmpty()) {
                startTimer();
            }
            snakes.put(Integer.valueOf(snake.getId()), snake);
        }
    }

    public static void startTimer() {
        gameTimer = new Timer(SnakeTimer.class.getSimpleName() + " Timer");
        gameTimer.scheduleAtFixedRate(new TimerTask() {
            @Override
            public void run() {
                try {
                    tick();
                } catch (Throwable ex) {
                    log.error("Caught to prevent timer from shutting down", ex);
                }
            }
        }, TICK_DELAY, TICK_DELAY);
    }

    public static void tick() throws Exception {
        StringBuilder sb = new StringBuilder();
        for (Iterator<Snake> iterator = SnakeTimer.getSnakes().iterator(); iterator.hasNext(); ) {
            Snake snake = iterator.next();
            snake.update(SnakeTimer.getSnakes());
            sb.append(snake.getLocationsJson());
            if (iterator.hasNext()) {
                sb.append(',');
            }
        }
        broadcast(String.format("{'type': 'update', 'data' : [%s]}", sb.toString()));
    }

    public static Collection<Snake> getSnakes() {
        return Collections.unmodifiableCollection(snakes.values());
    }

    public static void broadcast(String message) throws Exception {
        Collection<Snake> snakes = new CopyOnWriteArrayList<>(SnakeTimer.getSnakes());
        for (Snake snake : snakes) {
            try {
                snake.sendMessage(message);
            } catch (Throwable ex) {
                // if Snake#sendMessage fails the client is removed
                removeSnake(snake);
            }
        }
    }

    public static void removeSnake(Snake snake) {
        synchronized (MONITOR) {
            snakes.remove(Integer.valueOf(snake.getId()));
            if (snakes.isEmpty()) {
                stopTimer();
            }
        }
    }

    public static void stopTimer() {
        if (gameTimer != null) {
            gameTimer.cancel();
        }
    }

}
